Mechanical and electrical vehicle obstacle detectors and particularly curb detectors, have been in use for a long period of time. The curb detectors which are used primarily to facilitate parking a vehicle generally employ a flexible probe that is attached near the front and back wheels of the vehicle. The probes are adjusted to rub against an obstruction, such as a street curb, with a predetermined clearance between the obstruction and the vehicle.
Mechanical curb detectors alert a driver that an obstacle has been reached when a rubbing noise, made by the curb detector, is heard by the driver by mechanical transmission. When electrical/electronic detectors are used, an electrical signal is produced when the curb detector strikes or scrapes against an obstacle such as a curb. The generated signal operates a lamp and/or a buzzer located in the vehicle's driving compartment to alert the driver that an obstacle has been encountered.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention. However, the following U.S. patents were considered related:
______________________________________ U.S. PATENT NO. INVENTOR ISSUED ______________________________________ 4,967,180 Wang 30 October 1990 4,904,894 Henry 4,870,868 Gastgeb 3 October 1989 4,855,736 Hsu 8 August 1989 ______________________________________
The Wang patent discloses a pre-impact alarm apparatus that signals the driver of a motor vehicle that obstacles exist in the path of the vehicle when the vehicle is backing-up. The alarm apparatus consists of a flexible sensing bar that projects from the rear of the vehicle. The bar includes an electrical impact head that is electrically attached to a buzzer located within the vehicle. When the sensing bar impacts an obstacle, the impact head closes a set of contacts that energizes the buzzer.
The Henry patent discloses a hail sensor that uses a plurality of piezoelectric transducer positioned to produce an output signal when it is vibrated by a hailstone. The transducer output is supplied to a conventional signal processing circuit such as peak detectors and counters, which detect the electrical signal produced by the transducers.
The Gastgeb patent discloses a sensing device which produces a response when the point of impact between an object and a member occurs at a preselected location on the member. The sensing apparatus includes a piezoelectric sensor that produces an oscillatory electrical signal which is proportional to the vibration in the member generated by the collision between the object and the member. Appropriate circuitry is provided for analyzing the oscillatory electrical signal and for producing a response if the object impacted the member at a preselected location.
The Hsu patent discloses an electronic parking sensor apparatus having a base for attaching to a vehicle. The apparatus includes a flexible probe for contacting an impending obstacle. The probe is electrically attached to an electronics alarm unit that includes a filter circuit, an alarm circuit and is equipped with a pair of 1.5 volt cells that supplies the power to the alarm unit. The filter includes a timer for activating the alarm circuit when the electrical signal continues beyond a first interval which varies between 0.05 to 1.0 seconds. The timer also prevents activation of the alarm unit beyond a second longer interval that varies between 10 to 40 seconds. Separate front and rear transmitter units can operate on different signal frequencies for separately indicating front and rear contact with the obstruction.